Unless you tell PBP to do otherwise, it's always going to drop code in the
hardware interrupt vector locations.

Try something like this;
Code:
DEFINE  INTHAND HIGH_INT  ' High Priority Ints
DEFINE  INTLHAND LOW_INT ' Low Priority Ints

ASM
HIGH_INT
   blah
   blah
ENDASM

ASM
LOW_INT
   blah
   blah
ENDASM
Now PBP will insert jumps to both of your .asm interrupt handlers at both high
and low hardware interrupt vectors.

If you use the BASIC ON INTERRUPT option, PBP will just drop a RETURN at
location 4.